The present invention relates to a solid-state image pickup device such as a CCD or CMOS image sensor used in a digital camera or the like.
Conventionally, a solid-state image pickup device such as a CCD or CMOS image sensor is utilized in a digital camera or the like and its application field expands. As the product becomes more downsized and lower-profile, a solid-state image pickup device which is more downsized and lower-profile is strongly demanded. In order to meet this demand, a solid-state image pickup device using a TAB (Tape-Automated Bonding) tape as described in, e.g., U.S. Pat. No. 5,506,401, is available.
FIG. 7 is a sectional view of a solid-state image pickup device described in the above reference. As shown in FIG. 7, in a conventional solid-state image pickup device, a TAB tape 2 with an insulating film 22 and copper leads 21 is adhered to one surface of a protection cap 3 with an adhesive 10.
The TAB tape 2 is connected onto bumps 6 formed on electrode pads 5 of a solid-state image element pickup chip 1, on which a plurality of solid-state image pickup elements 7 are mounted, through an anisotropic conductive film 9. Alternatively, the TAB tape 2 may be connected to the bumps 6 directly by ultrasonic bonding.
The solid-state image pickup element chip 1 and protection cap 3 are sealed at their peripheries with a sealing resin 8. The solid-state image pickup device using such a TAB tape 2 can be formed more downsized and lower-profile than, e.g., a wire-bonded ceramic package.
According to the conventional technique, however, since the thermal expansion coefficient of the solid-state image pickup element chip differ from that of the protection cap, the heating in the manufacturing process or changes in temperature during use warps the solid-state image pickup element chip. Among countermeasures to prevent this, a protection cap with a thermal expansion coefficient comparatively close to that of silicon as the main material of the solid-state image pickup element chip may be used.
However, because of the cost and other characteristic aspects, a protection cap with a thermal expansion coefficient largely different from that of silicon must often be used. Therefore, another solution has been sought for.
When the protection cap and solid-state image pickup element chip are sealed at their peripheries by heating, air between the protection cap and solid-state image pickup element chip expands by heating and escapes from the sealed structure. If encapsulation is completed in this state, air in the sealed structure that has been restored to room temperature shrinks, and a warp occurs in the solid-state image pickup element chip. As a countermeasure for this, a portion free from the sealing resin is reserved in advance so a vent hole is formed there after adhesion, and this portion is closed later on and encapsulation is completed. In this case, however, the process increases, leading to an increase in cost.
Shrinkage of the sealing resin itself during hardening also warps the solid-state image pickup element chip. When a warp occurs in the solid-state image pickup element chip in the above manner, the focal point differs among the pixels of the solid-state image pickup elements, and the image quality degrades.
It is, therefore, an object of the present invention to provide a solid-state image pickup device in which a warp does not occur in the solid-state image pickup element chip.
In order to achieve the above object, according to the present invention, there is provided a solid-state image pickup device comprising a solid-state image pickup element chip on which a plurality of solid-state image pickup elements are mounted, and a protection cap provided on a light incident side of the solid-state image pickup element chip and adapted to protect the solid-state image pickup element chip, characterized in that the solid-state image pickup element chip is formed on a substrate with a thermal expansion coefficient equal to that of the protection cap, and the substrate and the protection cap are sealed with a sealing resin.
According to the present invention, there is also provided a solid-state image pickup device comprising a solid-state image pickup element chip on which a plurality of solid-state image pickup elements are mounted, and a protection cap provided on a light incident side of the solid-state image pickup element chip and adapted to protect the solid-state image pickup element chip, characterized in that the solid-state image pickup element chip is formed on a substrate made of the same material as that of the protection cap through a light-shielding layer that shields light, and the substrate and the protection cap are sealed with a sealing resin.
More specifically, according to the present invention, the protection cap and solid-state image pickup element chip with different thermal expansion coefficients are not directly adhered to each other, so no warp is caused in the solid-state image pickup element chip by an ambient temperature change.
According to the present invention, the solid-state image pickup element chip is sealed between the protection cap and substrate, and is not fixed to the protection cap. Thus, even when the atmospheric pressure in the sealed structure changes or the sealing resin shrinks during hardening, no warp occurs in the solid-state image pickup elements.